The biology of papovaviruses of the SV40-polyoma subgroup will be studied. The prevalence of BK and JC viruses in transplant recipients and the possible role of these viruses in complications in these patients will be investigated. The mode of transmission of the newly recognized papovavirus from the stumptailed macaque will be examined. BIBLIOGRAPHIC REFERENCES: K.V. Shah, R.W. Daniel and J.D. Strandberg: Sarcoma in a hamster inoculated with BK virus, a human papovavirus. J. Natl. Canc. Inst. 54:945-950, 1975. J.M. Reese, M. Reissig, R.W. Daniel and K.V. Shah: Occurrence of BK virus and BK virus-specific antibodies in the urine of patients receiving chemotherapy for malignancy. Infection and Immunity, 11:1375-1381, 1975.